How Sewing Machine Works - I'd alway wondered. In fact, as a schoolboy, I struggled to understand the mechanism, and now, with this animated gif, I get it...I think...WAIT! There's something wrong with this picture.

Does the bobbin in the center float? For this illustration to work, it must. The path of the upper (green) thread wrapping around looks wrong...It looks like half of the green thread is pulled in front of the bobbin, and the other half pulled in back of the bobbin. But if that were true, wouldn't the back path meet an obstruction of whatever is holding the bobbin in place (assuming it's not floating)...Perhaps, the path of the upper green thread is wrong -- both halves' are wrapped forward to the bobbin...I'm not sure if that would interfere with the basic idea or not...I think it would still work...but maybe not.

It's like one of those magic tricks. You think you've figure it out and...I better go find a sewing machine and figure this out once and for all.

The bobbin floats! - I investigated further and found that the bobbin does in deed float, at least on some designs, so the animation is accurate. Below is an illustration that helped me understand.

Step Two is getting the top thread to go round the bobbin. This is done by the hook coming across at the right time and catching the top thread and pulling it around the bobbin case and bobbin. This process is shown in figure 1 & 2. Figure 1 is without the hook, bobbin case and fabric. Figure 2 is with the hook, bobbin case and fabric.